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Holley’s Mid-Mount Accessory System is the LS Swap Answer

An accessory drive solution for any LS swap situation

Wes Duenkel May 4, 2018
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Newsflash: GM’s excellent Gen III and Gen IV (often lumped together as “LS”) small-blocks are great for engine transplants. They make great power, don’t weigh a ton, and are so compact it’s hard to find an engine bay that won’t accept one. Since everyone is doing it, it must be easy, right?

Well, the cussing starts when you want your LS engine to do more than just spin the transmission. The LS engine is plenty compact, but the stuff bolted on the front is usually anything but. Most LS accessory options fit into three problem categories: ugly, impossible, or expensive.

Holley solved all three problems with their new Mid-Mount Complete Accessory System. Finally, an accessory drive solution for any LS engine swap situation. It’s a complete water pump, alternator, power steering, and air-conditioning package that matches the diminutive exterior dimensions of the LS engine.

But the Holley Mid-Mount Complete Accessory System isn’t just about where the accessories are mounted, but how they’re mounted. Everything attaches to the innovative water pump casting—nothing bolts to the cylinder heads.

Having struggled themselves with LS engine swap headaches over the years, Holley’s designers took a clean sheet approach with their latest accessory drive solution. It’s clear that Holley replaced, rethought, or reengineered everything.

Take the alternator. While its mounting provisions are common with a fourth-generation Camaro, the battery stud is on the side so it fits tightly to the cylinder head. The alternator’s unique casting utilizes the latest hairpin/square wire, six-phase technology to deliver 150 amps.

Below the alternator is a Type II power steering pump, which includes a brilliant banjo to -6 AN hard line adapter. The piece relocates the pressure outlet to make the installation compact and plumbing a breeze.

And there’s no need to ditch the comforts of cold air conditioning with the Holley Mid-Mount Complete Accessory System. It includes a compact and modern SD7 compressor that bolts to the water pump casting with a handy slotted mount.

Speaking of the water pump casting, it includes a proprietary pump insert using the same technology from the latest Corvette, including a complex ceramic fluid seal to survive the rigors of high-rpm operation.

Besides including provisions for all of the accessories, the sophisticated, patent-pending water pump casting includes two heater hose mounting options to accommodate virtually any engine compartment situation. Additionally, the casting accepts standard and swivel thermostat housings.

The Mid-Mount Complete Accessory System is offered with a proprietary but OEM-style crankshaft damper (PN 20-185) or a “Premium” kit with an ATI crankshaft damper (PN 20-180).

Considering an LS engine swap? You’re officially out of excuses. CHP


The Holley Mid-Mount Complete Accessory System for LS engines includes an alternator, power steering pump, and air-conditioning compressor that all mount to a sophisticated, patent-pending water pump casting.


The water pump casting accepts both straight and swivel thermostat housings (swivel housing sold separately), and two heater hose locations maximize installation flexibility.


Holley offers kits with two different crank dampers: an OEM-style (left), and an SFI-approved assembly (right).


The kit we installed on a 5.3-liter swapped ’69 Camaro used the Holley OEM-style damper (left). Though it appears similar to a truck damper (right), the pulley is roughly 3/4-inch longer to position the accessories in front of the cylinder heads.


The 5.3-liter-swapped Camaro used a Corvette front accessory drive. While everything fit, the setup was messy and cumbersome.


The Corvette accessory drive positioned the power steering pump awfully close to the upper control arm.


Likewise, there wasn’t much room between the air-conditioning hoses and the inner fenders.


This photo says it all. The Holley Mid-Mount Complete Accessory System (top) is dramatically more compact than the Corvette system (bottom).


We began the process by installing the Holley harmonic damper with a special tool we borrowed from our local auto parts store. (Don’t try it without one or you could strip the threads inside your crankshaft.)


The included thermostat housing and side heater hose ports worked best for the ’69 Camaro.


The cartridge-style Holley water pump is a similar design to that used on the LT4 engine in the Corvette, though the two are not interchangeable. The internal ceramic seals are designed to survive sustained high-rpm operation.


The sophisticated water pump casting bolts to the block using OEM-style gaskets.


Holley’s 150-amp alternator tucks in tightly to the water pump and features the latest “square wire, six-phase” technology.


To make the power steering pump installation as compact and simple as possible, Holley designed this unique adapter tube that utilizes a -6 AN fitting.


We used a power steering pulley installer borrowed from a local auto parts store to install the pulley. Don’t even think about installing it any other way!


The power steering pump tucks up nicely under the Holley alternator.


While the air-conditioning compressor is a common SD7 unit, the mounting method is unique. The slotted inner mount makes installing the compressor a breeze.


The spring-loaded belt tensioner installs just below the air-conditioning compressor.


With all the accessories mounted, we installed the included serpentine belt.


Holley also offers a nifty steam tube kit, which includes brilliant blocks that rotate to accommodate virtually any engine configuration and intake combination.


The Holley Mid-Mount Complete Accessory System occupies virtually half the space used by the Corvette system.


For those that are aesthetically inclined, Holley also offers a billet aluminum cover kit for the pulleys and tensioner.


With everything buttoned back up, the Holley Mid-Mount Complete Accessory System is right at home in the bay of this ’69 Camaro.


There are now acres of space between the power steering pump and the upper control arm.


On the other side, the space gains are equally as impressive. Maybe enough room for a turbo or two in there ...

Photos by Wed Duenkel


Holley Performance Products
Bowling Green, KY 42101



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